Method of gravel packing well treatment



METHOD F GRAVEL PACKING WEI-JL. TREATMENT Douglass R. Davis, Houston,Tex., assign-or to Texaco Inc., a corporation of Delawarev Filed Dec.12, 1957, Ser. No. 702,356 2 Claims. (Cl. 166-15) This invention relatesto a method for the treatment of wells. In accordance with oneembodiment this invention relates to the gravel packingV of wells. Inaccordance with another embodiment this invention relates to anoperation, wherein a well is gravel packed and, if desired, fractured insubstantially the same operation.

In the production of petroleum from a petroleum producing formation onediiculty sometimes encountered, particularly when the petroleumproducing formation 1s an unconsolidated formation, that theproductivity of the well becomes reduced after a period of time due tothe sanding up or plugging of the well. To avoid this reduction in wellproductivity due to the Well sanding up it has been proposed heretoforeto gravel pack a well. In a gravel packing operation a filter bed ofporous granular material is deposited within the well bore adjacent thepetroleum producing formation. This porous gravel bed serves to supportthe adjacent petroleum producing formation and tends to prevent the wellfrom standing up due to the transport of finely divided solid materialfrom the producing formation into the well bore.

Recently it has'been proposed, see patent application v Serial No.401,159 filed December 30, 1953, now issued as Patent No. 2,814,347, thedisclosure of which is herein incorporated and made part of thisdisclosure, to carry out a gravel packing operation and formationfracturing operation substantially simultaneously. The operationsdisclosed therein, however, are complicated and require the use of arather large amount of equipment and production tubing or conduit.

It is, therefore, an object of this invention to provide an improvedmethod of well treatment.

It is another object of this invention to provide an improved method ofeffecting gravel packing and formation fracturing substantiallysimultaneously.

Another object of this invention is to provide an improved method ofgravel packing a well.

Still another object of this invention is to provide an improved methodand apparatus suitable for use in pressure gravel packing a well.

Yet another object of this invention is to provide an improved wellcompletion assembly or apparatus.

How these and other objects of this invention are accomplished willbecome apparent in the light of the accompanying disclosure made withreference to the accompanying drawings which schematically illustrate anembodiment of the practice of this invention particularly useful forcarrying out a combination well gravel packing and fracturing operationand wherein Fig. 1 schematically illustrates the operation and asemblyof apparatus in the initial stages of an operation in accordance withthis invention and wherein Fig. 2 schematically illustrates a completed-gravel packing-formation fracturing operation carried out in accordancewith this invention.

In at least one embodiment of the practice of this invention at leastone of the foregoing objects is accomplished. v

In accordance with this invention it has now been discovered that animproved well completion operation is obtained by disposing a wellscreen or liner within a well bore adjacent a petroleum producingformation and then carrying out a subsequent gravel packing operation insuch a manner that the material (carrier liquid and granular material)employed in the gravel packing operation is introduced into the wellbore into contact with the petroleum producing4 formation undergoingtreatment via ythe production tubing. The production tubing aftercompletion of the well treatment or gravel packing operation is thenemployed to carry the produced petroleum from the resulting treatedformation.

Referring now to the accompanying drawings and to Fig. 1 whichschematically illustrates an operation in accordance with this inventioninvolving gravel packing in vcombination with formation fracturing thereis shown a well bore 11 provided with casing 12. As illustrated in Fig.l, the casing 12 terminates within well bore 11 above the petroleumproducing formation 14. Provided within casing 12 is production tubing15. Removably attached to the bottom end of tubing 15 is well screen orliner 16 which is disposed within well bore 1'1 adjacent the petroleumproducing formation 14. Well screen 16 is releasably attached to thelower end of tubing 15 which is provided with back pressure foot valve17 schematically illustrated in Fig. 1. A packer 18 positioned aroundthe upper end lof well screen 16 provides a fluid-tight seal betweenwell screen 16 and casing 12. Further, a packer 19, such as a ring typepacker, is provided in the annular space between the interior of theupper end of well screen 16 and tubing -15 and provides a fluid-tightseal therebetween. Also, in fluid communication with the upper end oftubing 15 is production conduit 20.

Referring now in detail to Fig. 2 of the drawing wherein the samereference numerals employed with respect to Fig. l have been employed todesignate the same elements, there is schematically illustrated thepetroleum producing formation 14 after having been treated in accordancewith the practice of this invention. More particularly, Fig. 2schematically illustrates that petroleum producing formation 14 has beenfractured to produce a fracture 21 extending radially outwardly from thewell bore 11. The fracture 21 is shown as having been lled with a massof porous gravel 22. This mass of porous gravel material also occupiesthat portion of the well bore surrounding the outside of well screen 16.As illustrated, well packer 18 is positioned to provide a fluid-tightseal between the outside of well screen 16 and casing 12. Well screenring type packer 19, however, although in substantially the sameposition as illustrated in Fig. 2 now provides a fluid-tight sealbetween the inside of the upper end of Well screen 16 and the outside ofthe lower end of tubing 15. Further, as illustrated in Fig. 2 the oneway check valve or back pressure foot valve 17 at the bottom of the wellscreen is closed.

In an operation in accordance with the practice of this inventionwherein a petroleum producing formation is gravel packed a mixture ofcarrier liquid and granular material, such as sand or finely dividedgravel, is introduced via production conduit 20 into tubing 15. Thismixture is discharged from tubing 15 via back pressure foot valve 17located at the bottom of well screen 16. A sufficient amount of liquid,together with granular material, is introduced to ll the annular spacebetween well screen 16 and the well bore 11. The carrier liquid willtill the interior of well screen 16 since well screen 16 is slotted orperforated and therefore is in direct uid communication with thesurrounding annular space. The granular material, however, remainsoutside well screen 16 within the annular space since this material istoo large to pass through the'slotsor perforations of well screen 16.Further, since packer 18 and well screen ring type packer 19 are closedback flow of the mixture of carrier liquid and` granular materialupwardly into casing 12 is prevented. Pressure, by suitable means suchas a pump (not shown), such as fluid pressure exerted'by liquid fillingtubing 15,is then exerted upon the liquid filling the interior of wellscreen 16 and the surrounding annular space. The exerted pressure issuflicient to force at least a portion of the mixture of carrier liquidand granular material within the annular space surrounding well screen16 into the petroleum producing formation 14.

Desirably the pressure exerted upon the mixture within the annular spacesurrounding well screen 16 is sufficient to fracture the petroleumproducing formation 14. When a fracture occurs, as illustrated in Fig.2, at least a portion of the mixture of carrier liquid and granularmaterial is forced into the formation, the granular material occupyingfracture 21. Sufficient pressure may be exerted upon the mixture withinthe annular space surrounding well screen 16 to enlarge the resultingfracture 21 to any desired extent.

Since the interior of well screen 16 and the annular space within thewell bore surrounding Well screen 16 are in direct liuid communicationsubstantially the same fluid pressure would exist within the well screeninterior and the surrounding annular space. Further, with packers 18 and19 positioned as illustrated in Figs. 1 and 2 the fluid pressure exertedupon the liquid within the well bore surrounding Well screen 16 isreadily maintained and exerted substantially exclusively against theproducing formation 1-4 undergoing treatment.

When the petroleum producing formation 14 has been gravel packed, anddesirably fractured, such that there remains a fracture 21 within thepetroleum producing formationwith gravel 22 deposited therein, as wellas a residue or bed of granular material Within the annular spacedefined between well screen 16 and the adjacent petroleum producingformation 14 as illustrated in Fig. 2, the pressure exerted upon themixture within the annular space surrounding well screen 16 is released.Tubing 15 is released from the bottom of well screen 16 as by turningtubing 15 at the same time closing the back pressure foot valve 17.Also, the well screen ring type packer 19 is released and the tubing 15lifted to the desired position illustrated in Fig. 2 and then packer 19again set to provide a fluid -tight seal between the inside of wellscreen 16 and the lower end of tubing 15. Following the aforesaidoperations the well is swabbed and petroleum production resumed from theresulting treated petroleum producing formation 14 via fracture 21, themass of gravel 22 therein, well screen 16, tubing 15 and productionconduit 20.

Although the drawings show the well bore 11 penetrating the petroleumproducing formation 14 to be an open hole it is pointed out that thepractice of this invention is applicable to a cased formation whereinthe petroleum producing formation is provided with a perforated casingand the like. When the petroleum producing formation is provided with aperforated casing the mixture of granular material and carrier liquid isforced into the petroleum producing formation via the perforations inthe casing and the fluid pressure exerted through these perforations issufficient to fracture said formation.

Various iiuids may be utilized as the carrier liquid employed in thegravel packing operations in accordance with the practices of thisinvention. These uids include the normally liquid hydrocarbons, crudepetroleum, lease crude, petroleum fractions, crude oil or kerosene,lease crude or petroleum fractions such as diesel oil or kerosenethickened with a suitable thickening or gelling agent such as sodiumpalmitate (Napalm) and the like. Aqueous liquids, such Vas water,thickened or unthickened with additives which increase the viscositythereof and reduce fluid loss, as Well as brines, such as formationbrines, might be suitablyemployed as a carrier liquid in a gravelpacking operation described herein.

As will be apparent to those skilled in the art many modifications,changes and alterations are possible in the practice of this inventionwithout departing from the spirit or scope thereof.

I claim:

l. A method of treating a well in which a well screen provided withopenings therethrough is disposed in the well bore opposite a petroleumproducing formation to define a first annular zone between said wellscreen and said formation, the interior of said well screen encompassinga second annular zone in iiuid communication with said first annularzone and adjacent thereto which comprises introducing into said firstannular zone via a fluid fiow path extending from the surface downthrough said second annular zone to the bottom thereof a mixture ofcarrier liquid and granular material of a volume equal to the sum of thevolumes of the first and second annular zones, said second annular zonebeing the space within said well bore between said first annular zoneand said fluid flow path extending therethrough, said openings in saidwell screen being of a size to prevent the passage of granular materialtherethrough from said first annular zone into said second annular zonethereby providing carrier liquid only in said second annular zone,directing iiuid under pressure via said fluid flow path to the thusintroduced mixture within said rst annular Zone to exert a pressure onliquid therein suicient to force some of said mixture comprising carrierliquid and granular material into said formation while at the same timemaintaining substantially the same fluid pressure upon said carrierliquid in said second annular zone as is exerted on said liquid withinsaid first annular zone during the aforesaid pressuring operation,leaving within said first annular zone granular material to form afilter pack between said formation and said Well screen, adjusting saidfluid flow path so that said fluid flow path extends from the surface tothe vicinity of the upper end of said well screen, and producingpetroleum from the resulting treated formation via said filter pack,said well screen, and said fluid ow path, said second annular zoneduring the aforesaid pressuring operation being substantially free ofsaid granular material.

2. A method in accordance with claim 1 wherein the pressure exerted uponsaid liquid within said first annular zone is sufficient to fracturesaid formation.

References Cited in the tile of this patent UNITED STATES PATENTS1,994,816 Gray et al. Mar. 19, 1935 2,198,573 Davis et al. Apr. 23, 19402,207,334 Reynolds et al. July 9, 1940 2,243,967 Layne et al. `lune 3,1941 2,814,347 MacKnight Nov. 26, 1957

